The biggest advantage in taking pics in raw is the fact that there is no processing done to the shot by the onboard camera computer. When you shoot in jpeg, the camera processes the shot and tweaks it for color, exposure, etc. When you shoot in RAW, you get exactly what your shooting. The raw files are also much larger. I have the 300d and my raw files are about twice the size as the largest jpeg (6.3 mp).
Lastly, most graphic designers I work with (I'm in the marketing business) they prefer to utilize raw images when designing stuff because it gives them better flexibility to manipulate the shot.